Many people who fly would agree that airline travel has gone to the dogs. And in some cases, they mean it literally.

In the past few years, too many passengers have stretched the meaning of service animals that do vital jobs for their owners to include all manner of odd or ill-behaved pets.

Take the large, mixed breed canine on a San Diego-bound Delta flight last June that attacked the man in the neighboring seat, leading to 28 stitches and scars on his face.

Or the big brown pig that acted like one by defecating in the aisle and howling before being booted from a US Airways flight.

United Airlines turned down a woman’s request to bring her “emotional support peacock” onboard a flight leaving Newark Liberty International Airport on Tuesday.(Photo: Deseret News Hive)

Or the "emotional support" peacock that thankfully was turned away this week from a United flight at Newark Liberty.

Now one of the major carriers, Delta, is making a welcome move to rein in these unpleasant and even dangerous situations before airline cabins get even more zooey.

The biggest change: Starting March 1, passengers with psychiatric service or emotional support animals (ESAs) will need to provide proof from a doctor or a licensed mental health professional that they need the animal and certification that it is trained to behave — all 48 hours before any flight.

It's about time. Delta says it flew about a quarter-million service and ESAs last year, up 150 percent from 2015. This uptick just happens to coincide with the growth of online businesses that promise to connect pet owners with a mental health professional who can provide a letter certifying that the owners need a support animal to assist them. Broad federal law and regulations require airlines, except in rare circumstances, to accommodate such animals for free.

Inconvenience to others is just one part of the problem. Another? When these animals misbehave, they make life harder for people with traditional service animals trained to carry out specific tasks, such as dogs that guide blind people. Or psychiatric service animals that work with less visible disabilities — for instance, sensing an oncoming epileptic seizure or soothing a veteran with post-traumatic stress disorder.

Service dogs are trained to work, sit quietly, stay calm in stressful situations, and not defecate indoors — all reasonable requirements to join humans in airline cabins.

ESAs often fail these basic tests, and it’s hard to confer the same legitimacy on them when all owners need to do these days is find an online provider, talk, often by phone or Skype, with a "mental health professional," and get a letter attesting to their needs. Online come-ons from some in this new industry are pretty blatant: “Need an ESA letter?” says one. “Emotional Support Animal Letter Services — Don't Pay For Flights …"

The online industry is appealing to baser needs, such as avoiding the hefty fees airlines charge to take an ordinary pet into the cabin in a carrier. Delta charges $125 one way.

Some advocates for the disabled have lashed out at Delta for placing discriminatory burdens on people with service dogs. Finding the perfect way to balance airline safety and passengers' civil rights isn’t easy, but at least Delta is trying.

A lot of the problem is more about selfishness than necessity. The obvious solution: Pet owners should stop scamming, professionals should stop handing out letters so cavalierly, and the government should set stricter, more realistic rules.

Flying is already unpleasant enough. Passengers don’t need to share cramped rows with "emotional support" swine, turkeys or even nice dogs that aren't there to do a real job.

USA TODAY's editorial opinions are decided by its Editorial Board, separate from the news staff.